1. Field of the Invention
This invention relates to the field of molecular model systems and particularly to systems that include components molded of plastic material sufficiently resilient to permit them to be interlocked firmly but in such a way that torsion angles of at least some of the functional groups can be rotated without pulling the components apart.
2. Description of the Prior Art
Theory and experimental analysis have combined to establish that the atoms making up a molecule have certain geometrical relationship with respect to each other. For over one hundred years chemists have recognized that it would be valuable to be able to make accurate models of molecules in order to help visualize the structure and chemical nature of the molecules to see how they may be produced or modified. A model that can be visually examined and geometrically measured can offer an insight into the molecule that is an invaluable assistance to knowledge obtained by chemical analysis and study of X-ray defraction patterns. This is especially true in the case of macromolecules, such as the polynucleotides and polypeptides that are involved in living matter.
Descriptions of various types of molecular models are given in:
"The Use of Models in Stereochemistry", Ann Walton, Progress in Stereochemistry, 4, 335-375 (1968); "A Survey of Atomic and Molecular Models", Arnold J. Gordon, J. Chem. Educ., 47, 30-32 (1970);
"Some Reflections on the Use and Abuse of Molecular Models", Quentin R. Petersen, J. Chem. Educ., 47, 24-30 (1970);
"New Skeletal-Space-Filling Models", Frank H. Clarke, J. Chem. Educ., 54, 230-235 (1977); and
"Bipolymer Models of Nucleic Acids", Edward J. Barrett, J. Chem. Educ., 56, 168-169 (1979)
Those articles and the articles listed in their footnotes describe a wide variety of models from the early ball-and-stick models through the improved skeletal models, space-filling models, and framework molecular models (FMM). One of the purposes of the models is to represent the actual molecules as accurately as current knowledge permits, but this is not always consistent with other objects, such as clarification of geometrical relationships, including the internuclear distances and the torsion angles that exist between the nuclei of the atoms in the molecule. For example, the space-filling models show how the space between nuclei of a molecule is filled, bit it is quite difficult to visualize the internuclear distances and torsion angles in such models. It is almost impossible to construct some extremely complex molecules, such as t-RNA, of space-filling components. On the other hand, a Dreiding stick model shows distances and angles but does not give a realistic representation of steric volume.
Another factor that is particularly important in the case of macromolecules is the ability of the components of the molecule to remain properly interconnected after they have been assembled. The model structures shown in my U.S. Pat. No. 4,245,920 permit a good compromise between the technical accuracy of space-filling models, and the expository clarity of the skeletal models. Furthermore, the fasteners described in that patent link the atoms together so that a large and complex structure can be assembled with known angular relationships between the parts.
However, the torsion angles of at least the simpler organic molecules are not constant but continuously vary because of the fact that the molecules constantly receive heat energy. In order to see how a macro molecule may be varied, it is sometimes desirable to be able to combine a model of a smaller molecule with the model of the macromolecule to determine whether they can reasonably fit together and thus indicate that the actual molecules can be chemically combined. This may require the functional groups of the smaller molecules be capable of rotating relative to each other to achieve the desired fit with the macromolecule, and yet, it is so essential that the components of the small molecule be joined together longitudinally as accurately and firmly as the components of the macromolecule.
As in all molecular model systems, it is desirable that the components be capable of being produced inexpensively and assembled easily. It is essential that the components give accurate representations of the internuclear distances and torsion angles, and that components representing van der Waal's radii for outer atoms give a good representation of the geometry that exists in the actual molecule.